The present invention relates to a magnetic recording system using a rigid disk and, in particular, relates to a vertical magnetic recording system with high recording density.
As a disk type magnetic recording medium, there have been known not only a floppy disk using a flexible sheet made of polyester film, but also a rigid disk using a rigid (not flexible) substrate made of aluminium. A rigid disk is better than a flexible disk in high speed operation of a recording medium, and high density recording.
Conventionally, a longitudinal recording system in which magnetization is in the plane of a film has been used, together with a flying head. However, a longitudinal recording system has the disadvantage that the resolution or the recording density is not so high because of the presence of demagnetization even when the gap length of a head is sufficiently small, and the flying height of the head is sufficiently low.
On the other hand, a vertical recording system in which magnetization is generated in the thickness direction does not suffer from the demagnetization, therefore, the vertical recording system is promising for high density recording. In a vertical recording system, a magnetic anisotropic film which has easy axis of magnetization in the thickness direction, and the hard axis of magnetization in the film plane is used as a recording medium.
FIG. 1 shows curves between the flying height h.sub.1 of the magnetic head from the surface of the medium, and the recording density D.sub.50 (kilo FRPI; kilo flux reversal per inch). The curve L.sub.1 shows the characteristics of a longitudinal recording rigid disk, and the curve L.sub.2 shows the characteristics of a vertical magnetic rigid disk. The density D.sub.50 means the recording density at which the reproduced output level is 50% as compared with the level in a sufficiently low recording density. The unit FRPI (flux reversal per inch) means the number of magnetizations in an inch.
As shown in FIG. 1, the recording density of a longitudinal recording medium saturates when the height of a head is lower than 0.2 micron. On the other hand, the recording density D.sub.50 of a vertical recording medium increases exponentially as the flying height of a head is lowered. In particular, a vertical recording medium is superior to a longitudinal recording medium when the height of a head is lower than 0.2 micron (.mu.m). The vertical recording medium has the maximum recording density when h.sub.1 =0, that is to say, when a head contacts with a recording medium.
However, a prior recording medium has the disadvantage that when a head contacts with a recording medium, friction between a head and a recording medium in the relative movement of the head and the medium causes head crash, and both the head and the recording medium are destroyed within a short time. That is the reason why a flying head has been used in a conventional longitudinal recording system. In order to avoid head crash, the flying height in a prior art is larger than 3000 .ANG..